Changing of any other rapid transit line to heavy rail may require the same. In other words, nothing for another 4 years, which would delay the DRT as well. By which time, the question would become do we do the DRT before or after the others.
Changing Eglinton would require new subway trains but aside from that, the engineering work is already done for the subway tunnel.
Sheppard's EA is completed at least to Victoria Park, if not further (anyone know how far the existing EA goes?), although a new one would probably be needed to Downsview.
The only subway projects that need an EA are the DRL (obviously) and the Danforth line if they follow a new alignment to STC rather than the SRT alignment.