When Sport Pilot was developed, it was thought that training for ultralight pilots would be in Special-Light Sport Aircraft (S-LSA).
The FAA envisioned this timeframe would allow time for aircraft manufacturers to produce ultralight-like S-LSA in sufficient quantity to satisfy the need for ultralight training aircraft.
Unfortunately, such aircraft are not readily available in the marketplace. Presently only three manufacturers have produced an ultralight-like S-LSA — CGS Aviation Hawk, Higher Class Aviation, and M-Squared. In addition, the economy and lack of available financing have reduced the market for such planes.
EAA officials are working with FAA officials to allow the permanent use of E-LSA for training purposes with no timeline. It would improve safety due to increased available training vehicles and clear up confusion within the piloting community.
Read more about the issue here.