Uhh Borderlands 2 came out little over a year ago, why would they start another one when they are doing so well with the current game?
Games of that magnitude take 2-3-years, minimum, to produce, so if they haven't started working on 3 as of today...
(And there are lots of other engine options not named Unreal, which isn't really germane since you wouldn't be doing much heavy duty coding while in pre-prod--you can still set targets and start generating art, etc., even w/o a final engine in hand.)
(And my comment had nothing to do w/ it being fine or not my comment is that it's *bad business* to not be working on a third one *now*, especially after all the *other* horrid decisions of the last couple of years, i.e. you don't put the sure thing* on the backburner, and then plunge ahead into risky new ventures**.)
*BL3 is as close as it gets.
**Any new IP is much riskier.
EDIT: of course, this is working under the assumption they're not playing word games while working on a BL MMO and since it isn't called "BORDERLANDS 3" he is, technically, being honest and/or correct.