BlackBerry has announced that it will finally introduce its new Z10 touchscreen smartphone model in the United States next week, in conjunction with its AT&T program.

That’s about a month after sales of the Z10 began in the United Kingdom, Canada and several other countries.

Does this signify a comeback of sorts for BlackBerry?

If it does, it will be a dramatic reversal of fortune, as the company has been on a steady downward trajectory ever since the release of the first Apple iPhone in 2007.

But speaking as the owner of a BlackBerry device, I have to admit that the company has seemed to be hopefully behind the curve for quite a few years now. And this latest, last-ditch effort is coming up against stiff competition, such as Samsung’s new Galaxy smartphone which is debuting at the very same time.

BlackBerry’s recently installed CEO, Thorsten Heins, has stated publicly that the company has to regain some of its market share in the U.S. in order to be successful.

But the news on this front doesn’t look promising at all, as corporate accounts — long the company’s bread-and-butter busines– appear to be falling away.

In February, The Home Depot reported that it was replacing all of its company-issued BlackBerry devices with iPhones.

And just last week, Yahoo announced that it will be phasing out its app for BlackBerry devices as of April 1^st (yep, you got that right: April Fool’s Day).

Also, as of last September Yahoo no longer offers BlackBerry smartphone options to its own employees – just as with The Home Depot.

Rather than endorsements, these seem more like ringing indictments.

For those of us who love our BlackBerry keyboards, the company is promising that a keyboard version of the new smartphone (the Q10) will be available in the United States by this summer.

The question is, will it be too late by then?

We’ll know that answer soon.