Aside from your apparent saltiness, the crux to your non-explicit bone of contention in still entirely unclear... Regardless, there's an apt nearly 1:1 comparison that can be made with the MPC line. Akai as a business (after the assets were acquired) successfully moved on with the MPC as a platform after Roger's departure. Did they ever truly reinvent the wheel after Roger? No, but at the same time it wasn't entirely necessary either.
To me the questions are as follows:
Would the Tempest II benefit more from Roger's presence or rather a highly skilled programmer? Does Sequential even have a programmer skilled enough to pull it off? Could Roger release a revolutionary LinnDrum II and who's to say it won't be the next Linn 9000?
First of all, my "saltiness" is part of a longstanding and well-earned tradition around here, and the "crux" of the proverbial bone I'm picking is only unclear to you.
Secondly, with regards to Roger Linn and Akai, you wouldn't be so quick to use that as an example if you knew the dynamics of that situation, or the details of what has happened on either front since their parting of ways.
Thirdly, Roger Linn is working on the LinnDrum II as we speak. Indeed, there is a working prototype on his desk. But it will have more in common with the LinnStrument than any of his previous drum machines.
Lastly...
"Would the Tempest II benefit more from Roger's presence?"
Yes, absolutely without question, but that will never happen.
"Does Sequential even have a programmer skilled enough to pull it off?"
Let's just say the Tempest's OS was and remains the mess it is for a reason, and it wasn't Roger Linn's fault.
Cheers!