Also the NEC relied on XL turf. If we were playing on NPPL-style thin carpet over any tarmac (or the rocky NEC floor) people would have gone WTF...
I doubt the Millennium will use XL turf next year, much as I hate the idea, it just costs far too much I can't see it being sustainable - I do hope I'm wrong though.
As for being indoors at somewhere like Xcel - it will NEVER happen for any large scale event, we are too messy and treat venues with too much contempt, let alone the costs. The only time it will ever happen is a bespoke thing like the Mohegan Sun...
The lack of venues that combine our needs of space, access, surface, profile and "durability" to what we will do to them is one reason why I can't see us ever going above the second tier extreme sport that we are anytime soon. The cost jump isn't justified. ***Edit - unless we drop this idea that the lowest teams play the same event as the top guys ***