As an fyi: it's true Ryan and Pence were planning to run on the GOP ticket, but there was a reason for it. It was right after the "grab em by the pussy" comment came out. Any and all previous candidates would have turn tail and run from an election. Ryan/Pence thought for sure Trump would do the same, so they created an alternate ticket for the election, which was just weeks away. When they realized Trump wasn't backing down, they ended their plan. Nothing nefarious about it.
It wasn't to "off" Trump, if that's what you're implying.
Is Pence eyeing the top spot for 2020? No.
moar than likely