I've always wondered how everyone feels about a future Wario Land game. I personally don't know how I feel about the future of Wario Land, but I try to stay positive. Maybe Wario's 30th anniversary will give us something.
I always wondered why Wario wasn't in the New Super Mario Bros 2. That game is all about collecting gold, why the heck isn't Wario the main character, or running alongside Mario? Or even a rival? Seriously!
Also, I don't think Wario Land is doomed. I agree with @KingDragonWario in that we will get a new Wario Land soon enough. I hope it will be good. Wario Land: Shake it! was decent, and I wouldn't mind a very similiar game. Although I would love to get Wario's silly aesthetic back from older Wario Land games. Can you imagine Wario Land 4's gritty and hulking Wario in modern graphics?
There hasn't been a new game in a long while, but I think it's important to keep in mind how often Nintendo franchises sometimes go on hiatus.
Metroid had one in 1995-2001 and another briefer one in 2011-2015. Donkey Kong Country had no brand new installment in 1997-2009, Star Fox was MIA in 2007-2015. Kid Icarus also vanished from 1992 onwards, only to resurface in 2012 and go back on the backburner again right afterwards.
We will see another Wario Land at some point, the bigger question isn't so much if, but rather when.
I'm really not sure. I don't think Nintendo considers Wario Land to be a major IP anymore. Also, the last Wario Land game wasn't developed by Nintendo, and it's been 10 years since then (hard to believe. That game has aged better than Sakurai!). Wario Ware seems to be the more popular of the two Wario franchises, and given how much longer games take to make since the old days, I don't forsee Nintendo making one anytime soon. I don't think it's completely doomed, but just really unlikely that we will get one in the future. If anything we'll probably have to wait for Good-Feel to finish their current project or another developer to make one.