Now with the previous stated. I am going to make my point. In 10 years will gas grills still be used? Maybe a relic is a bit much, people will still use gas. BUT all the numbers in the BBQ industry point to pellet grills increasing in sales dramatically and gas grill sales decreasing in numbers.
I can attest to my own experience talking to people and selling gas grills myself, used to be I could sell an refurbished weber gas grill within days of listing, this is no longer the case. When people need a new grill there is a decent percent of them that will opt to go pellet over gas. They are simply too easy and the results are too good for people to ignore. Almost every conversation I have with strangers about BBQ ends up talking about pellet grills, most have seen them and most are intrigued by them.
As far as price coming down, people have been willing to drop 500 to 1000 on Weber gas grills for years so long as they know they are getting quality. On this note as well, the word is getting out, people are not happy with the new Weber gas grills, when I sell a used refurbished gasser I ask them their thoughts on the new Weber and I have yet to hear someone say "they are nice but too expensive" no they say the quality is so much worse than they used to be which is why they opted to go used.
So with those factors, 1. pellet grills are the wave of the future and 2. the #1 gas grill maker making a lower quality product the end results will be a shifting of the market to pallet grills and gas losing ground in the next 10 years.