I suspect if the takeover hadn't happened, the FOSS systems landscape would look a whole lot different. Like what, I don't know, but definitely different.
NeXT was acquired by Apple. 6 months later... Jobs was in charge, and history unfolded.
But does/did Solaris have anything worthwhile to offer over BSD/Mach.
Sun was in bad financial situation at that point, there is a high chance all these engineers would be laid off 8 years earlier if takeover hadn't happened.
It's possible IBM would have been a significantly better steward. Of course, it would have been hard to be a worse one.
That's a bit unfair. IBM would have probably canned hardware (and hence Solaris) much earlier than Oracle did, because they already had their own offering in that space and they were as invested as Oracle in Linux (ok, they don't have their own RedHat clone, but they are definitely big on supporting Linux).
IBM was buying Sun because of Java, and planning to chuck the hardware out one way or another. Oracle bought Sun because of the hardware and basically kept everything else going, albeit in a reduced fashion where there was overlap (MySQL) or they were not interested in the niche (OpenOffice).
I think Oracle had some decent ideas and didn't execute well on them, partly because of cultural issues. I don't think IBM would have done better, certainly not on the hardware/Solaris side. They would have probably done a bit better with Java/OpenOffice but that's about it. Solaris was doomed by the Linux boom, there is very little anyone could have done about that by the time the acquisition became inevitable.
They were interested in OpenOffice ... just not sustainably, as it turned out.
I am actually surprised they invested into Solaris for so long, considering its long time half dead status on the market.