People should already be at Tier 4 by now. I am currently at Tier 3 and will get to Tier 4 on Wednesday. I only run the projects once a day and not the second after they are done. So there should be people ahead of me.
First people to unlock Tier 5 on Holodeck will be in about two weeks - the progression system just cant get people there any faster. It's possible someone could have unlocked it on Tribble, but I have not heard of anyone who has bothered.
The torp at Tier 4 has a placeholder in it right now, and should be patched in with the correct version shortly. Given that, the code for the cannons might not even be in the game yet either. We'll just have to be patient.
EDIT: The T4 Romulan Hyper-Plasma Torpedo Launcher is being patched to Tribble as I type this, should be on Holodeck next week at the latest.
They wouldn't have been able to unlock T5 yet. You're looking at 100k Rep XP. Even sitting on the 20hr (remember they did not start that way) timers, they wouldn't be there quite yet.
As is, the Hyper-Plasma is not in the game yet - there's a "placeholder" torp there that's not part of the set- so no bonus. It's in the Trib notes for today that it's been replaced - so the stats might be available for it from somebody on Tribble.
As for the store unlocks, the Romulan Plasma are Plasma damage with both a Disruptor and Plasma Proc. They're not Disruptors with a Plasma Proc like the mission weapons - they're Plasma with a Disruptor Proc.
The cost of the Mk XI are 20,540 Dil while the Mk XII are 28,540 Dil...each.