I suspect you're overestimating the impact of bond rates on VC or IPOs. What does the data say? IPOs have declined during a period of low rates, and at first glance there doesn't appear to be any clear correlation between inflation-adjusted IPO size and interest rates. Know of data that says otherwise?
Even A16Z lists a bunch reasons IPOs are declining (in a period of low rates), none of which seem related to bond rates: https://a16z.com/2017/06/19/ipos/
That is the expected result. Firms can take longer to pay off because the cost of capital is lower, and VCs are under less pressure to deliver. What you'd want to see research on is IPO returns accrued to investors.
This study finds that low rates were correlated with less IPOs, not more: https://www.researchgate.net/publication/5184917_Interest_Ra...
Even A16Z lists a bunch reasons IPOs are declining (in a period of low rates), none of which seem related to bond rates: https://a16z.com/2017/06/19/ipos/