Your description of mages or former mages who have learned to live in a mundane world, but see hope on the horizon at long last (i.e. more mana will become available) sounds as if you might be remembering the plot of "Mana from Heaven" by Roger Zelazny. It has been reprinted in collections of Zelazny's stories, but originally saw print as the final story in the anthology More Magic, which was itself a follow-up to the anthology The Magic May Return. Both of those books resulted from Larry Niven's willingness to invite other SF/Fantasy authors to play around in the universe he had created to explore the premise that mana (magical energy) was a perishable natural resource and that our distant ancestors had used up most of the readily available stuff (on or near the surface of the Earth) before they began to realize their civilization was starting to collapse for lack of fuel to maintain the great spells upon which so much depended.
Zelazny's story seems to have been placed last because of simple chronology: It is the only story in that volume which is set in modern times. The other tales all seem to be set thousands of years earlier, when everyone still knew that the magic was going away, and that the Fall of Atlantis (for instance) was a well-documented historical event, rather than the ancient myth which it would later become.
Zelazny chooses to work on the theory that even as late as the 20th Century, a handful of expert sorcerers still remember lots of old spells and are able to use them for personal comfort, and even to keep their own bodies essentially immortal . . . if they are very, very careful not to run out of mana. (Of course they are also very careful not to flaunt the fact that they have supernatural powers which might make billions of other people jealous.)
The first-person narrator is currently called "Dave," but his more permanent nickname among his fellow sorcerers is "Phoenix." Others are called "Cowboy," "Werewolf," "Priest," "Amazon," "Gnome," "Dervish," and so forth.
As the story opens, Phoenix has been working for some time in a museum (I believe in Los Angeles), and we quickly learn that one advantage of this job is that the museum's agents often purchase cultural artifacts which were created by primitive societies around the globe . . . and some of those artifacts were loaded up with mana in previous generations . . . but now nobody in those tribes remembers how to cast any spells which would drain the mana. Therefore, whenever a new batch of acquisitions arrives at the museum, Dave checks everything over and grabs the good stuff for himself. You might say he's building up a stash of storage batteries to help feed any spells he needs to cast. (What he takes, we gather, is only a tiny portion of all the artifacts that flow through the museum, and Dave is able to avoid detection. Possibly by magically hypnotizing people to make them forget any discrepancies -- we later learn that he uses such spells when it suits his purposes.)
Zelazny indulges in some irony early on, by showing us how technology has reached the point where some of Dave's magic can now masquerade as modern science. In this scene, Dave and his girlfriend Elaine (who doesn't know about his centuries of experience as a sorcerer) are preparing to drive off in his car. Dave recently received an anonymous threat over the telephone and has reason to believe another sorcerer is stalking him with intent to kill, so he is taking extra precautions.
I paused about a hundred feet from my car and jammed a hand into my
"Watch," I told her.
The engine turned over, the car vibrated.
"How . . . ?" she began.
"A little microwave gizmo. I can start it before I get to it."
"You afraid of a bomb?"
I shook my head.
"It has to warm up. You know how I like gadgets."
Of course I wanted to check out the possibility of a bomb. It was a
natural reaction for one in my position. Fortunately, I had convinced
her of my fondness for gadgets early in our acquaintanceship -- to
cover any such contingencies as this. Of course, too, there was no
microwave gizmo in my pocket. Just some of the stuff.
I feel no need to spell out the entire plot of this story for you, but it involves a discussion of what you remembered: The mages are becoming aware that the future is looking brighter and brighter from a spellcaster's point of view.
Specifically: by the end of the story, it has been established that, in the past decade or so, each year's cumulative fall of meteorites onto our planet (particularly during the annual arrival of the Perseids) has been delivering significantly more new mana to Earth than was previously the average annual increase for thousands of years, and some sorcerers who try to measure these things are convinced that our solar system is now entering a particularly mana-rich region of the Galaxy. Since so few trained sorcerers are currently alive to use up some of that new energy (Zelazny makes it seem as if there are only a few dozen, but I don't think he commits to a grand total), the general level of magical "background radiation" worldwide is expected to keep rising and rising. Until once again it could be commonplace to see really big, flashy spellcasting taking place on a regular basis. Of course, this could mean history would repeat itself if a growing community of sorcerers used up the readily available supply all over again . . . but Zelazny has Dave point out that the current sorcerers are painfully aware of the mistakes of the distant past, and also that modern technology is getting closer to being able to send people to other planets, and then the mages could start gathering up all the excess mana from uninhabited places such as Mars and Venus.