If the convention chooses Ryan, the ultraconservative wing of the party will feel betrayed and will stay home.
How we have gotten to a point where Paul Ryan is somehow insufficiently conservative is downright frightening. This is the guy who was put on the ticket because Romney supposedly wasn't conservative enough. The same Romney who ran in 2008 as the conservative alternative to McCain.
Conservatism isn't the right word for the ideology of the American right wing. More like reactionary or counterrevolutionary.
Revolutionary, maybe? They're certainly the ones setting the narrative, as opposed to reacted to some "revolution."
But yes, the shift undergone by the Republican party since 2008 is dramatic, to say the least. The best way to think about it, in my opinion, is to view 2009-2016 as the GOP elites losing control of "their" party to the masses, whose fears Trump and Cruz are skillfully tapping into.
Personally, I expect US politics to continue moving along this path from elite-run puppet shows to mass politics. I would not be surprised to see both Democrats and Republicans be captured or fragmented by these mass forces over the next five years. By 2020 we may well see party formations which echo the communist and fascist movements of the 1930s.