Well, considering James Polk is the only Speaker of the House that ever became President, I don’t think it’s too likely.
One reason is probably that the position of speaker hold perhaps even more power than the President, and with a potentially unlimited term. So who would want to give it up?
First of all, is Johnson the real deal? Has he been tested? Dunno.
If he turns out to be the real deal, then I want Trump to pick him as his VP almost ensuring his election as President in 2028.
Polk was elected President and did not ascend from the speaker’s chair directly to the executive role.