Allow me to paint a scenario to help guide the answering of this question...
A Stegadon charges a unit of high elf swordmasters. The impact hits kill 5 of them. High Elves would get to attack next since they're always strike first. However, the 5 impact kills have made it so that they have nobody left in base to base contact with the steggie... so no elves get to attack. Now, does my steggie and crew still get to attack even though nobody is in base contact, but there was at the beginning of the combat?
A Stegadon charges a unit of high elf swordmasters. The impact hits kill 5 of them. High Elves would get to attack next since they're always strike first. However, the 5 impact kills have made it so that they have nobody left in base to base contact with the steggie... so no elves get to attack. Now, does my steggie and crew still get to attack even though nobody is in base contact, but there was at the beginning of the combat?