This depends in great part on who you talk to, but I have had both clients and students investigate these approaches with the pretty much uniform conclusion that there is more NOT provided in them than is provided. In some cases, you still need to build the cooling system, which is the biggest challenge in data center design today to begin with. At least one comes with the servers already installed, so they had better be what you want. At least one is well configured for both power and cooling, but doesn’t leave all that much room for computing hardware. It’s a question of what fits your needs.
In short, there are certainly applications for all of these packaged approaches, but the best applications right now seem to be for either temporary expansion or “swing space” for a move. Will it become the “thing of the future”? I wish my crystal ball was that good, but nothing I’ve seen so far strikes me as likely to be that widely adopted. Flexibility is important for today’s data centers, and the concept certainly provides flexibility in terms of modularly adding space without major building construction. But most people need highly flexible and adaptable space inside, which these solutions, at least the ones I’ve seen, don’t really seem to provide.