I guess it depends on the rip fence that comes with your saw. The fence that came on my 80's vintage Casedei sliding table saw weighs about 60-70lbs, puts my commercial Biesemeyer fence to shame and is extremely stiff. I would wait until your new saw comes in then evaluate the fence. Just like regular table saws I am sure sliding table saws come with a wide variety of different fences of differing quality and stiffness.
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The fence has a bearing mounted on an eccentric that allows my to raise the fence high enough to clear most saw dust issues.
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My saw has a 52" sliding table. I have just started using the saw and still have to make a sliding table fence for it. So far if the cut is under 50" I clamp the piece to the sliding table. If the rip cut is longer than 50" I use the rip fence that came with the saw. For breaking down whole sheets I still use my track saw.
All the advice I read on sliding table saws kind of boiled down to: don't buy any accessories for your saw until you actually have your saw and have used your saw. Everyone's usage will be slightly different so you need to find what works best for you.