New answer for more recent in-canon events:
More recent events in new!Who canon suggest that Gallifrey may return, especially as it is not in a time lock as previously understood but another universe (or possibly a "bubble universe", much like that which the House once occupied...).
As such, it would be possible for there to be new Time Lords.
Even without this, however, there is (as Michael Edenfield pointed out in his answer) no reason the Doctor cannot attempt to start his own tradition of Time Lords, especially if he can find or make a new Untempered Schism (which, while it seems to have been used as a rite of passage for all Gallifreyans, is also clearly tied to the Time Lord Academy). It is clear that species other than Gallifreyans are able to become Time Lords, as the Classic Who companion Ace eventually left the TARDIS to study on Gallifrey, with the eventual aim of doing exactly that, so this is not an obstacle.
It should, however, be noted that if any such new Time Lords were to have their own TARDISes, either the most recent object to referred to as the Eye of Harmony would have to be transplanted to somewhere whence its power could be transmitted across all of space and time (and to turn out to have been the one that used to sit under the Citadel on Gallifrey, which was in just such a setup) or the Doctor would need access to the Hand of Omega with which to create a new one. Otherwise, while it would be possible to grow new TARDISes from "TARDIS coral", they would have considerable difficulty obtaining power.