*You* will unlock nothing without researching it. However, *other companies* will probably unlock it *for you*... As long as you are willing to pay for the patent.

You don't *have* to research, *but* the tech may be unlocked more slowly than you would like (if nobody deems it worthy of immediate research), and you may find yourself having to pay money to access the tech level you want to use.

As far as I know, tech does not get unlocked "eventually" unless somebody specifically researches it, but with so many AI companies somebody eventually will.

ICBW,OC

You always have access to the second most recent level of research, regardless of weather you researched it or not.