Listen, I've been burned before on investments, once as a kid, collecting stamps, and twice as an adult in market crashes. No investment is ever truely safe. I'd say the cue collecting is an especially unsafe investment, as the recruitment to pool is so low and there is so much competition for peoples money these days.
Nostalgic baby boomers with tons of expendable income drove the cue prices up to an artificially high point at one point in time and as they slowly die off, lose their expendable income because of US health care policies, or simply lose interest because of old age, the cue prices will continue their downward trend until a bottom/ground floor is reached. Naturally other countries don't have policies that lead to financial ruin when you get old and sick and have more age groups involved in buying/selling cues as well as playing pool seriously, so these countries will probably have a more gradual decline in their pricing. Asia will of course prop up the cuemarket to a certain extent, as they have for a decade or more now. Old people buy cues in the US, but of course in Asia the market is more healthy and have some younger people involved. The Asian market favours expensive makers (expensive for the sake of being expensive) so the pricing will be very top heavy with little midrange to speak of.
Ordering from aging cuemakers is a risky policy, they might die before your cue is completed. Oh, please don't give me any of this sanctimonious nonsense! Every one of the collectors are circling around waiting for this or that maker to die or retire, like vultures! Of course we all pretend that nobody thinks like that, but that's the reality of the situation. If the guy dies, his stuff will be worth more. It's the nature of the collecting business.
There will always be an interest in the absolute greatest makers, but ivory policies etc makes trading them inconvenient and I think many such bans and restrictions will come in the future as well, especially on tropical hardwoods. Cues for playing will probably be made of carbon, anyways.
Invest in something with better odds of giving a return, would be my advice, but of course I have terrible luck in investments, so you better do the opposite
.. If you want a fancy cue from a famous maker, then go right ahead, but make sure you use money you don't necessarily need to get back.