Too true! But at least we'll get some new story missions. Maybe some new costumes everyone can use? Anything that isn't straight grinding. As to what happens when you get to lvl 50 though.... while I cannot speak for others I can pretty much guarantee "I" will not be grinding on a Rom alt all the things I'm grinding on my fed main. Its just NOT going to hapen. Can you imagine starting a brand new fleet starbase at this stage? Talk about demoralizing! Besides, we haven't really heard if its a third faction or if they took a page from Blizz and have lvl 50 Rommies join Starfleet or the KDF "to keep fighting for their people's freedom" or somesuch. It would even make sense if they plan future arcs to revolve around figuring out what's going on (OMG, is that plot advancement in STO??!!), and then going about stopping it.
We will probably have joined STF queue. I suppose they'll find a reason why, maybe Sela saw the Iconians plot, and, reluctantly, joined forces with the Feds and KDF. Could also explain why it's not an Empire anymore, but a Republic.
Don't want to grind? Take your time for your reps. I still have many chars not T5 and i'm fine with that. They'll go at their own pace. Don't want to level up another starbase? Join a mega 500 active people fleet (and be active). Who cares if it's not a fleet of friends? It's still better than joining the Fed or the KDF.
The Somraw, K'tinga, D'Kyr, D7, Kumari, Xindi carrier, Xindi escort, and the T'Varo are all older than the Constitution Refit and yet they are tier 5. The Constellation is made up primarily of Connie refit parts and it is tier 5, there is no logical reason whatsoever for the no tier 5/6 connie rule.