I remember hearing ths before and being somewhat bemused. By this time next year I imagine I'll be wanting to purchase on Blu-ray exclusively (I already am with almost everything except documentaries and anime - DVDs are losing thier value to me by the day) and so if it only comes out on DVD next year they may well lose a sale they would have made to me had they brought it out today.
I know I'm not the only prospective buyer out there for Ocean Waves, but I am one of those who have been waiting for Optimum to release it for, what... must be into years now? As Zin5ki points out, it's hardly aimed at the kiddy end of the market Ponyo is going for. Along with Only Yesterday it's likely to sit squarely at the "Collectors" end - and as a collector, I'm not going to be paying a tenner for a single film in standard definition by next year. I'll either wait for it to drop to a bargain basement price or import the inevitable Japanese Blu-ray, because it would likely take another decade for us to get that.