pjc: in most of the applications where the classic T5s were used in the past, the PLs replaced them.
PLs have better electrodes design and efficiency, which is harder to make for such a small lamp, in a linear format.
In Israel currently, exit signs and emergency lighting, are almost the only application, were the classic T5s are still popular, although LEDs starting to replace them also in these applications.

So to answer my own question, so to speak, the eventual phase out of the classic T5 will probably be driven by the market. As more PL and LED fittings replace the classic T5 fittings, the demand for the T5 tubes will drop to the point where the manufacturers will stop production. This process has already started with exit signs turning to LED. As has been stated, it will probably take years before the phaseout happens.

and as often as 40's/50's/60's old stock still shows up i doubt if they would dry up anytime soon even if all production stopped right now.i needed a bunch of 4 and 8w tubes for slot machines.ordered some online in bulk.they were all 60's ge's.guy had hundreds of cases of them.

In the U.S., classic T5s are still frequently found even in new undercabinet fixtures.  In fact, some manufacturers have product lines with fixtures that span both ranges. PLs seem to be used less frequently in this application, although I own a such a fixture.  PLs are just a bit bulkier, and people typically prefer a very low profile fixture that won't be visible.  Halogen, xenon, and more recently LEDs are also popular in these applications.  As an alternative to T5s, some shorter fluorescent fixtures can be found with proprietary T4 or T2 lamps, but these are still far less common than regular T5.

It seems like (upon my own observation) that the heyday of T5 preheat fixtures for "low-profile" undercabinet lighting and similar applications occurred in the 1970s.  Since the millenium, T4 fixtures have become popular for the same applications.  However, T5 lamps are still more readily available, it seems.

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lol 

lol >.<

Haha, that's really funny.... . I kind of wonder if some people ever read comments back to themselves before posting them.

It's hillarious. Nobody at all agrees with "LightingExpert235" (His user name needs questionning) anyway, but he still thinks he knows it all lol

@ Al, I see you have temporarily put your Beta2 up, Looks nice! :-)

Hi Dan, yep I put it up for the picture but I have to be careful as the landlord lives next door and technically I'm not supposed to be making 'alterations'  . In November I move into my own place so I'll be able to put up all my lights PERMANENTLY 

Oh i bet you can't wait, i for one will be keeping an eye out for any photos ... Have you managed to get the large starter fitting working then since i sent the starter?

Hi Dan, no I haven't yet but I will shortly; that fitting is the last one to do up and I need to get more cable first as I used it all up on the other three I've done so far. I found a date code on the capacitor in the fitting I need the large starter for, September 1947!

Hi, Oh wow 1947! that means its 64 yeas old this month  i think thats the oldest Fitting i have possibly come across on here... Ok well good luck with your Refurbisment on it

Dan