Planning To Retire By Age 50

46-year-old Anderson Silva says he's got about 4 years of fighting left in him ... telling TMZ Sports his plan is to hang up the gloves before his 50th birthday.

Oh, and he's down to box Jake Paul!

Let's start with the YouTube star turned 4-0 boxer who just beat Tyron Woodley ... who's long been rumored as a possible opponent for the UFC legend.

"Everything is possible. Jake Paul and Logan are doing a lot of good work in this new entertaining show. We'll see. Everything is possible. I respect both. [Jake] is doing good, working hard. So, we'll see, maybe this is possible too."

Silva -- who's boxing Tito Ortiz on September 11 on Triller -- is only a few months removed from defeating 35-year-old…