If you spend too much time and energy “planning” and making grandiose promises of “things to come” will anyone really care or notice?
With Facebook “pages” there is little to be gained from putting up a “holding page” – you can simply choose not to make your page public, so you can tweak settings and layout privately.
With Twitter, however, it’s not that evident. Granted, you could choose to “protect” your updates, but you wouldn’t be able to hide your profile page and if you plan on using Twitter for your business “protection” may seem odd.
There has been plenty written about what Twitter is and isn’t, but ultimately if you don’t actually use it nobody will either notice or care.
Of course, conversely speaking, if you used it badly people would notice and probably criticise you …
However if your business’ Twitter status is frozen with a “coming soon” style tweet, then maybe you’ve really misunderstood the medium completely. A blank account would probably seem saner.