I seriously doubt Extreme would only take the IP and not some people as well ... obviously it could happen like that, but they would at least need a small percentage of support staff initially, until their team absorbs the technology anyhow. If you examine both company's portfolios, there is a lot of product overlap .. not 100%, but close. So, 100% retention is unlikely. And, for those who do stay on-board, it's unlikely there will be a 1-1 salary match when they move over to Extreme.
My guess - Extreme will retain the current overseas contractors, plus 20-30% of the 'local' engineering staff. JMHO. YMMV.