Wentz had a good rookie year and even if he wasn't top 10 as a rookie I think mostly everybody would give the 2nd over all pick some time to see if he can be top 10.
Foles is a backup so I don't think anyone expect to have a top 10 QB as a backup same as keenum.
Smith isn't top 10 and his replacement was drafted and Smith is gone.
If Bortles remains the starter its only for continuity purposes because you can bet if they have a shot at a Drew Brees or Cousins, they would happily cut Bortles if the cap allows it.
Mariota had a good rookie and sophomore season and a bad 3rd year so no reason to give up on him yet after only 1 bad year out of 3.
All are good points but are contrary to what the "draft a QB every year" crowd blathers on about. Here are some other QBs that are not top 10 and haven't been replaced:
Flacco, Dalton, Palmer, Newton, E.Manning, etc. etc. etc.
What about Derek Carr? One winning season out of three. Should the Raiders draft his replacement?
Simply look at the numbers. 22 QBs every year are not in the top 10 (BTW, some of those are veterans that need a successor). Let's say half are young and the team is still waiting. That means 11 teams (or more) are looking to draft a QB early every year to find that elusive top 10 QB. It doesn't happen because it makes no sense.