Hanyu - 1st and 2nd at GP, 2nd at GPF, 2 at 4CC, 4th at worlds
Kozuka - 1st and 2nd at GP, 5th at GPF
Tatsuki Machida - 1st and 3rd at GP, 6th at GPF, 1st and 2nd at some B competitions
Takahito Mura 1st at GP, 8 at 4CC, 8th at worlds
I think men will definitely do just fine even without Takahashi and Oda.
With ladies it is a bit complicated. Kanako Murakami suggested that she may or may not retire because she wants to experience the 'normal student's life' However, when she is Japanese lady number 1, she may change her mind.
Kanako Murakami 3rd and 4th at GP, 3rd at 4CC, 4th at worlds.
Satoko Miahara has slightly struggled with underrotations and has been heavily deducted for that, but she has the full set of jumps and with a bit of work on the jumps she has the potential to be pretty decent. Her results even with the downgrades are not bad at all - 7th at junior worlds and 5th at JGPF. She needs a few years but she will be there pretty soon.
Then there is a few "average" skaters, such as Haruka Imai (8th and 5th at GP, 2nd and 3rd at B competitions), Risa Shoji was good the previous season in juniors but the last one was struggling (still in juniors), Rika Hongo (also still in juniors) could be promising (5th and 2nd in JGP and 9th at junior worlds).
So ladies will not be same as until now, there won't be 3 ladies in the first 5 or 6 at worlds, but they will retain one in first five for sure (Murakami), one with quite a lot of potential (Miahara) and any of the ones I mentioned above (Shoji, Hongo) may turn out to be reasonable too. Perhaps not the first 5 at worlds, but decent standard. I think that's still more than other countries (except of Russia and USA) will have.
Japan will be afected. Losing their superstars skaters Mao and Dai. The reteirement of Mao Asada will hit them financially no doubt about that. Korea it wilk take them years to have a world class skater like Yuna Kim. Italy has the same issue as Korea. The countries whi will benefit from the reteriments of the top 3 are US and Russia they have the talents to stand in the world podium
And I think Canada will benefit. But I will miss Japan's bevy of spectacular ladies, and of course the glorious Daisuke. And I hope that Korea is able to remain an important part of skating--if not right away, then in the near future.
Korea will be decimated without Yuna as she is the team really. The Chinese pairs will have to await see what happens to Sui and Han after Pang and Tong retire; and I am not sure what to think of Zhang and his new partner. Canada's men could be in trouble without Chan though Reynolds who is about the same age might stay on one would think and maybe change coaches and get a stylist and see what happens. The US team usually always has someone coming up in men's women, dance and even pairs or in the case of pairs a new combination. I would think pairs has little marketability as they keep changing partners almost as fast as Liz Taylor changed husbands.