I see that the question was a little more specific than I offered an opinion on above, that is will .com domain names go up in value.
Here are my thoughts/opinions on that specifically:
The most desired single words in .com will continue to increase in value, some dramatically
I think less common single words (but not like crazy specialized medical terms, for example) willselectively increase in value - but only those where a business or organization use makes sense
I think there will not be much motion up or down on double, triple word names, outside of some trending sectors going way up, or some sectors no longer meaningful losing most value. Prices may well keep up with inflation or investment returns in other instruments, but I don't see a doubling or tripling in the next few years.
I think the price of brandable (by that I mean not all terms used as brands, but only the subset of made up words, creative spelling, blends, etc) will marginally increase, but just more or less at same rate as other business expenses.
I think match type names, particularly those for narrow areas, are tough to call, and the most dependent on the details of search. I don't see a lot of growth in value, but many will hold their value, and many others will not. Match names that are also great brands will be strong, though.
I think some longer names that define a category that is increasing in importance, even specialized, may increase. Some companies will want to have the authority to own the term for that niche.
I see more marketing tied to users going to a campaign-specific website may drive increased demand and higher prices for common and creative phrases.
I don't know numeric, alphanumeric, or 3L/4L markets well enough to offer an opinion. Same for place names and names in general.
I am surprised how much names with traffic/link history are going for wholesale these days. I don't know that component of the market enough to know if those will go up or down.
These are just my opinions, in most cases subject to my own biases and not based on detailed analysis.