Las Vegas may seem frozen in time, what with one would-be Strip resort — Echelon — showing only as a barely started steel skeleton and another — Fontainebleau — a towering, empty building. Las Vegas’ construction gusto has been suppressed by the recession; the biggest developments in town are two large observation wheels. But once either of those is completed, a passenger high above the Strip may well look down on the construction of a sports and entertainment palace of one sort or another. It may be a sports arena downtown, next to the Smith Center for the Performing Arts. It may be an arena rising alongside the Strip behind Harrah’s and Imperial Palace, next to the observation wheel known as the Linq. It could well be a 50,000-seat, enclosed stadium at UNLV. Or it could be an arena on the south end of the valley, in .