I don't think I'd go much bigger when I look at ours. If you go with a larger tv, it can easily get in the way of the doorway or stove on either side. Included in the package price ($412 on our MSRP), the TV comes with a decent locking wall mount and allows the tv to swing around and be viewable at many angles.
We bought the TV that was included, no choice, as an option with this particular camper. I had mentioned in the negotiation that I only wanted the power package; tongue jack and awning, and that I could buy the tv elsewhere for $140 vs. the $412 they were asking. Anyways, they threw in the tv and you need to figure in the price of a wall mount that suits you.