回复：My current H1 will expire to 6 year limit...

if it can be extended, you can swith back when you extend your H1B.
you can extend your H1b beyond 6 year limit only if your I-485 is still pending.
If it is denied, you can ask reopen, I don't know if you can extend your H1B before your reopen request get approved.

You can think of filing a new I-485 before your H1b expire, then you can certainly extend your H1b beyond 6 year limit.