I don't think China will invade taiwan anytime soon. But this thinking that as long as China doesn't reunify with Taiwan then China is bottled up is wrong thinking for the Japanese and US. The key is China's military strength.Very important to remember that Japan's defence build-up is driven by CCP and Russian militarism. From Japan and USA's perspecitve, Taiwan is like a cork that keeps the PLA bottled safely within the First Island Chain. If CCP were to go after Taiwan, they'll definitely need to contend with Japan. It's not so much that Japan/USA need to defeat China in a war, they just need to deter the CCP from starting something in the first place. The last thing they want is the PLAN/PLAAF operating into the western Pacific from the East Coast of Taiwan.
If China is able to surpass US in military strength overall, would they be "bottled up"?
Instead they will overwhelm Japan and Taiwan with so much military exercises that they will basically give up. Suppose, they have 2000+ stealth fighters for example and 10+ aircraft carriers in the next 20 years, they will be circling Japan and Taiwan with constant carrier surveilence and fighter sorties.
This will be backed by thousands of Rocket force missiles, drones, laser weapons and so on.
China will do so much greyzone warfare that the entire first island chain will feel suffocated. They will either give up completely or do something outragous to start a war.