IMO if Turkey (a NATO member at present) blocked off the Bosporus to Russian Naval shipping, that Russia would invade Turkey even though Turkey is a member of NATO. That, more likely than not, would cause WW3.
That said, both Russia & China will likely offer all kinds of incentives for Turkey to leave NATO. The US has already alienated itself from the Current Turkish regime by harbouring the alternative President as evidenced in the failed coup (no doubt there are CIA fingerprints there) in 2019 against Erdogan.
IMO, this Ukrainian War has further implications for the region and in particular how Turkey may fair out which is currently sandwiched between the Ukrainian & Israeli wars.
