Okay, I will brag a little. I designed the first titanium springs ever used in a volume consumer product.(Mountain bike suspension)
I have no interest in it for a pistol frame, though.
Aluminum is strong enough for occasional use in carry guns, and heat treated alloy steel is stronger than titanium.
The best aluminums go about 75 - 85ksi ultimate tensile strength
6-4 Ti, when heat treated, can get up to about 150 ksi.
Beta Titaniums, used for springs, do get up to 200 ksi, but they are very expensive and hard to work.
Plain 'ol 4340 steel can easily go to 240 ksi tensile, and is still tough at that tensile strength.
Titanium has some rather odd habits - heat it up to 1000 degrees or so, it will absorb impurities from the air, from oil, even from the sweat on your skin - then become extremely brittle and crack.
For springs, we have to acid etch the surface of the metal, handle them only with clean cotton gloves, and then put the spotlessly clean parts in a high vaccum furnace, during heat treating. Touch it with your bare hand, put it in a furnace, it will break where you touched it.
An ultimate lightweight autoloader could indeed be an alloy frame with Ti slide, but you'd have to do some tricks to get it to cycle reliably. For the frame? No, it's the wrong material.