the reason it's 'done' is because it has lost its relevency; not enough folks lining up to buy it. when that happens: bye-bye. just like the binda toe straps, the old logo bars, the super record rears... this is one of those, "vote with your wallets" things. why should they make something that doesn't allow them to profit?
fwiw, i too, will miss it. but i think it is not the death knell for the types of bicycles that used it in their frames. for the amount of frames built this way, there are still many options. i like dedaccai tubing lotsandlots and even think the cromo version of 531 is as good or better than the mangymo.
these pipes all come in wide varities of diameters and guages.
e-RICHIE
Richard Sachs Cycles
No.9, North Main Street
Chester, CT 06412 USA
http://www.richardsachs.com
Tel. 860.526.2059