The new fixed speed XF pump is designed to be as efficient as possible at very high flow rates. It is primarily designed for use with large waterfalls and negative edge pools where very large flow rates are required. Rumors are that there will be a variable speed version of the XF eventually, and some people claim to have seen one, but there hasn't been any official announcement yet.
It seems very likely that the optimization required to work efficiently at very low flow rates, normally used with variable speed pumps, will have to be different from what they did in the XF. My assumption is that they will apply some of the technology that went into the XF back to the IntelliFlo, but optimized differently to be more competitive with the EcoStar. As of now there is no word of when of even if they will do that.