It depends. If it's still around in 10 years, I'd be willing to bet not a single line of code currently used by Facebook will still be running. Some startups will become "enterprises", because of what they do, but I'm talking about financial services, banks, government departments, public services etc. Their technology doesn't move forwards, because it can't. I'm sure little to no startups are using Oracle IAS (Internet application server), yet it's one of the most used technologies in enterprise applications, and will be for some time. If you're a sysadmin with a deep understanding of IAS, or Oracle DB, or HP-UX, or any of the countless other "old" technologies used in enterprise, you'll have a job for life.
