Well, in Tiberium Wars there was still the Juggernaut mech, and who knows, maybe the Juggernaut convinced GDI that mechs do, in fact, play a good tactical role, thus allowing them to allow the production of mechs again. Of course, knowing the faults of the previous predecessors, they decided to build a new model and ship it out into the battlefield (I noticed the Titans have thicker legs than the other ones, as well as their joints look more armored as well). All in all though, I think the Titan looks like a Rifleman from Mechwarrior.
I dunno, I'm looking forward to this game. Looks fun and action packed imo.