That sounds rather unlikely to be honest. Yes, a more right-wing candidate - Seehofer perhaps, or someone else - could gain back some votes from the AfD. But we'd be talking, what, a few percentage points? And how much would they lose in the centre in the meantime? If you ask me, at least as much as they'd gain on the right, and very likely more.
In the longer run it may be something else, especially if the AfD runs into the ground and breaks down into endless in-fighting like so many populist right parties in Europe, but if we're talking about new elections in the short term, I don't see how Merkel stepping aside solves anything.
When I said Lindner had to get over it, I meant with the current election results, and as a pragmatic conclusion rather than as a judgement of his policies or positions - for whatever reason, he was the one to walk out and not the Greens, otherwise I'd have said the same about the Greens.