Silicon at those temperatures is still not a gas. But more interestingly photosynthesis equivalents become drastically less efficient at those temperatures. Life could still extract energy from chemical processes or even light, but ecosystems would be energy starved which slows down evolution. On top of this the chemistry capable of supporting complex life is again less efficient than carbon based life at lower temperatures.

Net result you might get the equivalent of very simple multicellular life, but intelligence becomes extremely unlikely.

Yet, there are simple Si compounds that are gaseous at such temperatures.

Chlorophyll photosynthesis does not work well at high temperature, but that says less than nothing about whether photosynthesis of different products using a different molecule and a different process could evolve. What we can say is that if it could, it would, somewhere.

You have no basis beyond your own preconceptions for any statements about likelihood. Thus, your estimate is 100% confabulation.

> Yet, there are simple Si compounds that are gaseous at such temperatures.

Silicon tetrafluoride might be a gas, but it’s not going to be plentiful. If you feel there are real options here feel free to list em.

> that says less than nothing about whether photosynthesis of different products using a different molecule and a different process could evolve.

Carnot efficiency does. You can’t simply scale up temperature and expect equivalent efficiency.