It's not a case of 'he is or isn't'. It boils down to whether he has lied, or misled. All the indications are, that he has done both. So therefore he should resign.
Governments are a reflection of their populations. He'll be promoted. He's certainly receiving lots of support from his fellow MPs.
If he comes out, they'll be queuing up behind him offering their firm support. He's guaranteed to get a warm hand on his entrance.