1) Barry comes out of retirement after Umbrella comes after him to put him out of commision because he knows too much.

2) Steve isn't dead. Play Code Veronica X. He is possibly still alive(just like Ada was).

3) Last escape? Yes. Last round of breaking in and ass kicking? NO!

4) Leon maybe doing that but now that Ada is back he is once again throwen into the hurricane.

5) Hunk not only is in mini-games but many of the documents you read through out RE2,3 and CV

Long story short. They are never out of the game!