In my opinion, it’s very likely that modern sealed will go up in price. However, will it be enough to make up for storage, time, locked-in money that could be spent on other things, inflation, fees, being quite liquid (especially as prices go up), so much competition, etc? Modern, sealed might seem like a good investment in a vacuum. The question, however, should be: is modern sealed a better investment than other investments, incl. things outside the hobby? Or, is there a better way to spend your money than to put it into modern? Once you look at it from that perspective, it doesn't appear to be that obvious of a play anymore.
Also, the people making the most money in the hobby are not people holding sealed. They're people operating as a business, constantly buying and selling single cards. I think that most people holding some modern sealed will either lose money or break even at best down the road. People are impatient, life events come up and they sell, people get scared and sell at the wrong time, or maybe they even bought at too high of a price, etc.
Today's trends often become tomorrow's collectibles. If children now are as enthusiastic as they were during the early print runs, then great, there may be a future in contemporary Pokemon. I just don't see young children having the same enthusiasm as the WOTC era of Pokemon cards… the Red/Blue/Yellow Gameboy days. I do, however, see adults looking to take advantage of the Pokemon "investment" hype. So, my take is 'the cat is out of the bag,' and now that Pokemon is seen as an "investment vehicle," long-term growth will be impacted and likely corporate decisions within Pokemon will shift based on said hype.