If you are in the VC scene, presumably you have a decent amount of investment capital. I think what you need to focus on is not so much the equity selection (i.e. short/buy Twilio), but on asset class allocation. You should pick up David Swensen's Unconventional Success to understand the details of why asset allocation is by far the most effective method to maximize returns in the long run.
So, instead of shorting Twilio, you should be thinking about the expected return from the VC fund, and how to re-allocate your investments. I'd assume that the VC funds are giving you outsized returns in the recent years, so you should try to balance your portolio by making investments in the real estate, natural resources, mutual funds space, etc.