I'd imagine there would be little change in weapon technology between the 24th and 25th centuries but since the later half of the 25th century has not really been rendered in canon it is difficult to say what new advances would have emerged. We however can be assured that phaser arrays/cannons, photon and quantum torpedo and perhaps the addition of disruptors.
I would expect to see dark matter/energy beams, multiphasic shielding armor, and photonic canons (yes just as "The Doctor" envisioned in Voyager). I would also expect to see photonic life forms piloting holographic ships.
Given the time they had to study Dominion technology, it would be reasonable to assume that Star Fleet would have begun experimenting with poloron based weaponry, namely, phased poloron beams. And don't forget Voyager's tramsphasic torpedeos. Even though it was never installed, I'm sure Voyager's database still contained the data for the isokenetic cannon that Star Fleet could have studied and adapted.
Well Star Trek Online is set in the early 25th and they use...well everything.
Consider, the Federation has been using phaser technology for about two hundred years now, it's something that they're comfortable with and something that allows them to destroy and to disable which fits Starfleet's philosophy. Don't expect it to go anywhere but get more powerful. As for Phaser cannons or arrays....yes. Both, sometimes on the same ship, sometimes on separate ships. The Transphasic torpedo probably, though certain Star Trek books have proposed that they would only be held in reserve to deploy against the Borg as they hadn't adapted to it yet. Multiphasic shields are probable, though Starfleet had had that technology for about a decade as of Nemesis and hadn't deployed it on frontline ships, it appears they were focusing on Regenerative shielding. Perhaps Covariant or Paratrinic shields other technologies that Voyager encountered would be developed. I would guess Ablative Armor Generators would be in use though.
Until synthetic lifeforms, Androids and Holograms but especially the latter get more rights under Federation law, I doubt that Starfleet will let them have their own ships.
But if you consider the technology gap between the original NCC-1701 and the NCC-1701-B, that's 2267-2293 26 years, and the B was frontline for two or three decades, then the equivalent 26 year gap, Nemesis and the Enterprise-E 2379+26=2405 25th century. It won't be a huge jump. The late 25th....who knows? Rayfire 15:47, December 21, 2011 (UTC)
O'brien in the DS9 episode "Field of Fire" talks about a "regenerative phaser" being developed over the TR-116 slugthrower....perhaps they brought the 116 back too, who knows?
I recall seeing the USS Rhode Island firing phasers arrays in 2404 of the alternate timeline in the Voyager finale, "Endgame". And Star Trek Online is non-canon. - 18.104.22.168 22:39, December 21, 2011 (UTC)