I strongly suspect they're going to crunch in some other weapons that technically after 3049 but close enough - like Ultra/20 and such. It just seems logical from an update perspective.
As for 'mechs, when the Clans invade a bunch of new IS chassis come out around the same time, so I suspect PGI will be spending a lot of time making the first big expansion, coming out right on the heels of the main game; if they aren't already.
For the OP, here's what
not to expect:
ATMs
MRMs
Rocket Launchers
Heavy Lasers
Heavy Gauss
Light Gauss
Rotary Autocannons
X-Pulse Lasers
Thunder LRM ammo
Fan favorite MW4 'mechs (Uziel, Argus, etc)
Also, while it goes without saying, any Jihad era stuff is out (Snub-Nose PPC, HAGs, Plasma Rifles, etc.)
Also, Bushwackers are right around the corner and I suspect they'll make an appearance in the same update as the Clan invasion.
Edited by Victor Morson, 09 April 2012 - 11:14 PM.