Yes, and no.
The Ukrainian constitution limits the options on how a President can be impeached and put out of office. (pdf)
In short, without a court decision, he cannot.
But, and this is a big but. He can be declared unfit to continue as acting president due to absence.
In short. Since most of his regime fled the country and others resigned, the only acting legitimate body left was the parliament (Verkhovna Rada). Who then appointed new (and this is important) ACTING president, Prime minister, minister of internal affairs and speaker until next election on May 25th.
This means, in my opinion, that Yanukovych is still president, but not acting since he is declared in abscent. If he returns before the elections (i doubt he will) he will be prosecuted on the charge of mass-murder on the demonstrators of Maidan Square, impeached and overthrown in due process.
My conclusion is that he in practice, is overthrown. But not juridically, since he fled from prosecution.
That is my 5 cents on the matter.