'sdi' is only standard definition 720x576PAL 720x486 NTSC.

Can you find out what the cable spec is for HD-SDI?
And how far it goes?

Its going to be much shorter as the bandwidth is 6x greater.

So you will be unlikely to be able to use any sdi cables to go long distances with hd-sdi.

I suspect the short distance hdsdi cables go - mean people then consider having to use fibre and dvi.

The technology life cycles these days are between 18months and 3 years max.

Bettting on any technology outside this timeframe is not going to be a winning strategy.

Richard