This isn't so much a discussion about the future of Federation technology as it is about the future of Starfleet shipbuilding policy.
Personally, I think Starfleet will always have a mix of large multipurpose vessels and smaller specialized ships. The ratio will probably vary as conditions warrant, but Starfleet will probably need both kinds of ships to carry out its responsibilities to an ever growing Federation, IMO. I'm more inclined to think that the bulk of Starfleet in the future will consist of smaller vessels, but there will still be "big daddys" in the fleet too. But it's possible (I guess) that there might not be any ships larger than the Galaxy- and Sovereign-classes if Starfleet continues what appears to be a current trend of building smaller, more compact starships...
Personally, I think Starfleet will always have a mix of large multipurpose vessels and smaller specialized ships. The ratio will probably vary as conditions warrant, but Starfleet will probably need both kinds of ships to carry out its responsibilities to an ever growing Federation, IMO. I'm more inclined to think that the bulk of Starfleet in the future will consist of smaller vessels, but there will still be "big daddys" in the fleet too. But it's possible (I guess) that there might not be any ships larger than the Galaxy- and Sovereign-classes if Starfleet continues what appears to be a current trend of building smaller, more compact starships...