The E series looks nice, but it's not really a good platform for running PlecoDict since it doesn't have a touchscreen and hence there's no way to use a handwriting recognizer with it - this is another reason why we don't support Symbian, incidentally, as the vast majority of Symbian devices (pretty much any model that's not made by Sony) don't have touchscreens. Yet another reason is that Symbian is reportedly just as buggy as Palm OS and Pocket PC (if not more so) - there may be some slight improvement in hardware quality, as Nokia still has a pretty good reputation on that front, but aside from the less Windows-like interface I don't really see any advantage to choosing Symbian over Pocket PC, and it's much much harder to write programs for Symbian.
There's also the fact that the vast majority of our sales are still to people who are buying a PDA primarily or exclusively to run our software (and hence will buy one for whatever platform we support), which tends to diminish the interest in any new platform release - the Palm OS version of PlecoDict is still outselling the Pocket PC one by quite a lot, we think because of the combination of the lower cost of Palm handhelds and the fact that our "Which Handheld Should I Buy?" page strongly recommends Palm (along with the fact that the Palm OS version is considerably easier to install). Adding on Symbian would really only get us sales from people who already own Symbians or (like yourself) can't stomach getting a Palm or Pocket PC, and there's no way those sales would cover the cost of our developing a Symbian port.
So unless our sales grow by an order of magnitude in the next few years, or Palm and/or Pocket PC completely die out and Symbian eats their marketshare, it's highly doubtful that you'll see a Symbian product from us anytime soon.
As for other Symbian Chinese dictionaries, I'm not really aware of any but perhaps someone else might be able to recommend one. In general the Symbian third-party software market seems to be a lot smaller than the Palm / Pocket PC one, so there may not be a lot of options out there.