MWO 'Mechs won't happen due to licensing issues, as technically those 'Mechs are ultimately Microsoft's as they own digital BattleTech IP. Or, well, unlikely to happen anyway. Besides, why would they use MWO 'Mechs since the classics got new art?
Further lance packs will depend on how well the new box set sells, undoubtedly. And if it does sell well, then the likely contents for the lance packs are "more of box set 'Mechs" and "missing classics" (now that the lawsuit's over), of which there are several, at first anyway. EDIT There are 7-10 missing classics, depending if you count Osts or not (do remember Ostscout got new art and mini), more if the Goliath and Scorpion are added to mix. Mix the missing classics and box set minis with about two and two ratio and you can create quite a variety of lance packs.
Plus since the Commando, Awesome and Catapult got new minis, very distinct from MWO's models, other TRO3039 'Mechs getting new sculpts in the future isn't impossible. Provided the box set sells well and lance packs would contain more than the missing classics.
Of course, lance packs might not be on table even if the box sets sell well. Would 'Mech-only "expansions" sell well? Perhaps some other kind of thing might be more interesting products, such as small scenario packs that come with a 'Mech or two, similar to the new intro box? A map, a 'Mech or two, some fiction, some scenarios and appropriate rules.
Of course such things would likely make only one sale per customer, i know i'm not terribly keen on idea of having multiple copies of same non-miniature material, whereas multiple lance packs are just fine. On the other hand, a new 'Mech miniature would be nice incentive for getting a scenario pack.
But then again, this all depends on how well the box set does.