I'm not an expert of any kind, but I've come to similar conclusions about RLV architecture. Back in the very early days of the X-33 program, I made a number of predictions for what the first true RLV would look like (as opposed to the Venturestar):

1.) It will use kerosene or some other kind of dense fuel, not LH2.
2.) It will be TSTO, not SSTO.
3.) It will have axi-symetric tanks and a generally simple airframe (no bi-lobed lifting-body whatsits).
4.) It will be piloted.
5.) It will be either VTVL or HTHL, but not mixed-mode.

I'm not necessarily so sold on the last one any more, but I still stand by the rest, which would be nicely fulfilled by the biamese architecture you're talking about. I must admit that I'm a bit disappointed by the SLI's morph into the CTV: Boeing had sketched out what looked like a fairly interesting biamese system, and the LOX/kero engine developments were certainly a good thing. (Lockheed's "airplane orgy" proposal, in contrast, seemed designed to ensure absolutely NO commonality between the stages... on the other hand, it had "PORK!!!" written all over it, which was probably the point).

Anyhow, in the longer term future, I think that space elevators will be a better bet for opening up the mass exploration and colonization of space, and I honestly wouldn't be too suprised to see one being built in, say, 30-50 years. Our materials science should easily be there by then, and the estimated cost (I've seen numbers from $10 billion to $100 billion) wouldn't be much more than any number of other big-budget items. And the payoff...!

Cheers,

Nathan.