"Will the next generation of LED lights prevent me from purchasing the TK45 for $129?"
Same question about computers. There are always new faster CPUs, higher capacity HDDs, etc...so you can wait all your life if you care too much about the obsolescence of a product containing a modern LED or CPU, but one thing is sure, your TK45 will be as bright in 10 years than today so if you really need a flashlight with this brightness level, it's really up to you.
If you don't really need it, wait for 1 year, TK45 will be cheaper.
Simple.