It's been confirmed that it will have a definitive ending but do you want it to be "fixed" with a dlc?
Personally I want a
GOOD solid end to the main quest line, but am not too bothered as to whether or not it continues on afterwards with the proviso that it doesn't render my choices up until the end of the main quest line inconsequentual.
With regards to the definate ending being fixed, if they do decide to do that, I hope that they do not roll over and present us with a similar fetid pile of game breaking manure that was Borked Steel, which completely obliterated Fallout 3's designed game balance and forced all of your characters to end up with the same skillsets if you did not severely/obscenely gimp yourself in at least one specific stat and a lot of perk choices and even then it was hard not to become a J.O.N.T.M.O.A. (Jack of No Trades, Master of All) wasteland deity of destruction and general overpoweredness.