Probably another 10 or 15 minutes. An hour at the most.
Seriously: No one can say for sure, but considering that Sun is still offering the 1.2 exam, it's a safe bet that 1.4 will be available for quite some time. [ September 16, 2005: Message edited by: marc weber ]
"We're kind of on the level of crossword puzzle writers... And no one ever goes to them and gives them an award." ~Joe Strummer sscce.org
Note that many professional developers are not yet using 1.5. Indeed, many are still using 1.3 or even earlier. Why? Because old versions die hard -- especially in corporate environments where new versions need to go through extensive testing before becoming the "standard." In fact, some companies have a policy of avoiding the current version of anything. Often, change doesn't happen until they're forced into it. In other situations, old versions are necessary to work with other systems. For example, IBM's Lotus Notes runs Java, but still uses 1.3. (Just this week, I was forced to use Vectors in new code for precisely this reason.)
So 1.5 is cutting edge, but 1.4 enjoys a "real world" vitality. And I think the 1.4 exam will share this longevity.
(But again, without an official word from Sun, we can't be absolutely certain.)