they're kinda crashing i think (or atleast they were last time i cared about runescape hahaha) but id definately say its worth the investment because they're "rares" therefor people will always want them causing the price to rise in the future
a santa would be a better bet as they seem to be appreciating in value alot more. but with the EoC coming people are probably going to dump rares as people quit and others sell their gear for lots of pking stuff to test it all out. rares are a risky move atm.
yes when bot nuke is activated all of the rare items will probably go back up to the normal price or maybe even higher so I think you should invest this.