I agree with the lot of you before me. I wouldnt trust the Romulans as i think they'd see the Vulcans as weak and perfect prey.
Meanwhile, i would think the Vulcans who were so adamant about their heritage and culture before the destruction of Vulcan, would seriously want to keep their race and culture pure now.
But please correct me if i am wrong, i always had the impression that Vulcans and Romulans DID share some heritage...am i remembering wrong?
Yes, they two do share a distant mutual heritage.

The ancestors of the Romulan peoples (or "Rihannsu", as they call themselves) were originally Vulcans who rejected the peaceful, unifying, "logical" philosophies of Surak and left Vulcan many centuries past to establish their own colonies among the stars. They remain a Vulcanoid people, but left before the strong development of mind talents and subsequent mind control techniques Vulcans acquired in the intervening years.
The Rihannsu of the TOS and XI timelines are the cultural descendants of these more aggressive, emotional, war-like Vulcans that Surak fought to change before they destroyed themselves in conflict.
Physically, excepting the mind talents, Vulcans and Romulans are nearly identical (forget about those stupid prosthetics on the various TV series over the years - in TOS as in NuTrek they look a lot alike, thank goodness). The Rommies have the incredible strength and endurance of Vulcans, the same physiology - green blood, same organs etc. We know that they can interbreed. There's some dispute whether they go through pon farr. The Romulan language, although differing from native Vulcan, retains much of the original language, even some of the same words and phrases (much like modern English has echoes of Anglo-Saxon, Norse and French).
I wonder what the Empire thinks about Nero and his terrible revenge on Vulcan and the Federation - it will be interesting to see if this is touched on in the next movies. The Klingons are no doubt royally pissed at the Romulans for (as they see it) taking out 47 warbirds - I wonder if they'll be easily convinced Nero was a renegade acting on his own? Will that push the Klingons and the Federation into an earlier alliance? Or will Nero's escapapdes make so much trouble with the Romulan EMpire that they will seek negotiations with both Klingons and the Federation?? I'd really like to know what went on politically in the 25 years since Nero destroyed the Kelvin. It will be interesting to see what role Vulcan will continue to play in the Federation - they will surely re-establish the Vulcan Science Academy on the new world.
No doubt, there will be plenty to keep folks like Sarek busy in the next few years, in both diplomacy and rebuilding the culture.