GOP will impeach him sooner just to score points with the electorate and not get squished in the mid-terms.
Not before the damage is done.
A figure like Trump is politically useful for them at least in the short term, they can do all of the unpopular stuff-like gutting ACA without a replacement and blame him later when public opinion turns. The things that will negatively affect their base, the small business owners farmers and disenchanted rust belters are things the GOP desperately wants. Trump is the perfect fall guy.
Of course Trump is just as likely to blame
them when it all turns to shit. What a happy, fun bunch.