Did the broomstick industry stop research after the Firebolt?

Question

For the first three years of Harry's Hogwarts life, we see a new broom coming out as the fastest each year:

Several boys of about Harry’s age had their noses pressed against a window with broomsticks in it. “Look,” Harry heard one of them say, “the new Nimbus Two Thousand — fastest ever —”
_{-Harry Potter and the Philosopher's Stone, Chapter 5}

“Very latest model. Only came out last month,” said Flint carelessly, flicking a speck of dust from the end of his own. “I believe [the Nimbus Two Thousand and One] outstrips the old Two Thousand series by a considerable amount.
_{-Harry Potter and the Chamber of Secrets, Chapter 7}

“Just come out — prototype —” a square-jawed wizard was telling his companion.
“[The Firebolt is] the fastest broom in the world, isn’t it, Dad?” squeaked a boy younger than Harry, who was swinging off his father’s arm. “Irish International Side’s just put in an order for seven of these beauties!” the proprietor of the shop told the crowd. “And they’re favorites for the World Cup!” _{-Harry Potter and the Prisoner of Azkaban, Chapter 4}

There's no mention of a faster broom in any of the remaining books.
So, did the broomstick industry just stop their research after the Firebolt came out? Or were they unable to make anything better than the Firebolt?

Answer 1

The broomstick industry continued after the Firebolt

While we don't see much info about new brooms in Harry's later years at Hogwarts, Rowling's writings about the 2014 Quidditch World Cup show that plenty of new brooms have come out since the Firebolt.

The turning point of the game was undoubtedly the staggeringly powerful shot hit by Hongo, which smashed the tail off Nigerian Seeker Equiano’s broom. As Equiano span out of control, Noriko Sato soared through the middle of the action to seize the Snitch from the midst of distracted Nigerian players intent on saving their teammate. Japan pass into the semi-finals where they will meet Bulgaria.

The Nigerians have been riding the controversial Thunderbolt VII, a competitor to the Firebolt series, which many experts feel has sacrificed safety for speed. Professional brooms ought to be able to withstand all Bludger blows and an inquiry is already underway. Rumours that a posse of Nigerian warlocks is currently heading for the Thunderbolt Headquarters in Manchester, England, have not been confirmed.

_{Quidditch World Cup 2014: Japan vs Nigeria}

Besides the Thunderbolt VII, an additional four brooms appear in these writings:

• Varápidos
• Starsweeper XXI
• Yajirushi
• Firebolt Supreme

_{Quidditch World Cup 2014: Place Your Bets with Ludo Bagman}

Of particular note is the Firebolt Supreme, which seems to be implied to be a successor to the Firebolt (which no one seems to be using anymore).

It would seem that further broom research has continued since the Firebolt, as evidenced by the completely different brooms appearing in use twenty years later.