will this fit on the new d-Lite it?
The Rimelite Speed Ring for Elinchrom is not a particularly good design but, to answer the specific question, yes, it will fit the new D-Lite IT.
Please note that there is no provision for mounting the ring itself directly to a lightstand. The Grand Box and its speed ring must be attached to the strobe's accessory mount (the D-Lite in your case, a 600RX in mine). Consequently, the entire weight of the Grand Box must be borne by the light's accessory mount. With my 71" Grand Box, that weight is considerable. In addition, having the Grand Box hanging off the front of the strobe places a tremendous strain on the light stand's mount. Slippage can be an issue, especially with the D-Lites which do not have particularly robust stand mounts to begin with.
I have already contacted the manufacturer and suggested (strongly) that the speed ring be redesigned with an integral light stand mount (as is available from other manufacturers such as Falcon Eyes).
Apart from my speed ring issues, the Grand Box is a fantastic modifier. Using it is almost like cheating :-)