Wtih no "Swift Learner" perk, I had already hit the Level 30 cap by the time I installed and loaded "Dead Money". Thanks to being stripped of all of my gear, I opted to go with melee weapons (my absolute weakest skill) with the occasional Laser Pistol shot to take out emitters and the like. I took quite a bit of damage because of the up-close-and-personal nature of combat, low skill, the lack of armor and the Cloud, but never died from combat (collar blew lots of times, though). I got back to New Vegas just in time to hit Level 35 at the start of the final battle, which was a walk in the park by that point and also done mostly with melee weapons (yeah, I brought a knife to a gunfight - seemed like a good idea at the time :goodjob: ).
Adding more levels to that would be next to useless from a game perspective. The only reason I can see for doing it are for those players who must have 10s in all stats and 100s in all skills and I think there are some mods out there to let you do that without breaking it for the rest of us.
If I could have one thing from the devs in a DLC, I think I'd like to be able to keep playing after the final battle, but my understanding is that's a pretty solid "no".