They'll probably be getting Kleiza and Anderson back as well and they could be getting an SF back for Calderon, too.
Even if they're getting a 1st on top of that and get decent value for Calderon, without Ross, it's not enough. People can criticize Gay all they want, but they'll be hard pressed to find a better wing player, because they're too good to get a quality draft pick, few of that caliber are available in free agency and when they are, Memphis is not exactly known to be a prime destination. Davis is a nice prospect, but with Arthur in tow, I don't see how he get's more than 12-15 mpg max.
On the flip side, because Ross is not in the trade, Johnson and Davis are somewhat redundant and Toronto is also not exactly known to be a prime destination for free agents either, it's a worthwhile gamble for the Raptors. Because it's them and Colangelo, it'll probably blow up in their face though.