First off don't forget about the Altman Shakespeare. They already have their answer to the S-4. Nobody's using them, but they have had their own version for a long time.
I think the more interesting question is Why aren't ETC and Strand trying to compete with Altman when it comes to fresnels, strips and Cyc lights? As was mentioned in a thread a while back wouldn't it be great if ETC made a real fresnel that you could pop an HPL 575 into and have one lamp to stock in your inventory. Altman is still very much the king of the not so sexy (strip and wash light) end of the conventional instrument world and I think they are quite happy to be there. Remember that the 360 was the most popular instrument on the market 20 some years ago. I think perhaps after getting their clocks cleaned by that upstart ETC they are perhaps a little conservative in their business model now.
Altman's future appears to be the connection with Colorkinetics and their LED par. ETC and Strand don't have an LED instrument yet do they? Altman's has been making them for what 3 years now? The Altman booth at LDI was all about the LED PAR. I wanted to get some info on strips and other gear and it just wasn't there. So my guess is that they are comfortable with what they already do really well and instead are focusing on taking the lead in a new direction with LED technology.