I think the declining BTC value of BCH indicates the market is pricing in the increasing odds of 2MB Bitcoin blocks becoming reality.
Most likely. There are two separate beliefs that could lead to this:
1) the belief that 2MB is good enough, thereby reducing the advantage of 8MB; and
2) the belief that the sum of the value of S1X and the value of S2X at time = t0+ will be greater than that of the SonlyX at t=0- (much like the BCH split resulted previously in a larger aggregate value).
I think the declining BTC value of BCH (I suppose that's the altcoin you meant) indicates that a certain gang thinks their money is best burned supporting the next attack, so BCH purchases are being phased out.
I doubt it, but I must admit it is plausible.