I don't see May resigning, and I don't see Johnson being made PM if she does, in the wake of his serial, public idiocies.
The worst outcome I can see is fumbling the Brexit negotiations by whichever lame duck PM, while a polarized UK is riven by political infighting, further terrorist acts inciting a rightward drift (which amazingly did not happen in the election, so who knows).
Also: this election (and the US') shows that the influence of the news media is rapidly waning in the facebook era.
EDITED: 9 Jun 2017 12:37 by DSMITHHFX