I think this may be true - but not with non-major moves in the price of BTC.  The alts seem to claw up soon after every BTC spike up - implying the orchestra keeps playing for alts while BTC rises or stays strong.  On WallObserver everyone keeps saying 'The end of alts will come with the ultimate rise of BTC' but this 'wipe out and return to BTC' is just NOT happening as they expect.

I don't disagree with ArcticMine but I think it's not one sided; BTC and alts are currently symbiotically linked - but therefore it looks like an overall crypto market bubble - the two parts of the market are ebbing and flowing and feeding each other.   

If BTC were to collapse steeply and go into a bear market, I don't think alts would keep up their current USD values at all - I don't see how they could when their 'cash out value' is basically linked to the worth (and expected worth) of BTC.

So your theory is correct in that the overall market is ultimately BTC-dependent, as is the value of alts - irrespective of the (agreed) differences and genuine alt growing partial autonomy from BTC this time.

If BTC does not (badly) crash but continues to rise, so will the alts and it could go far higher with all the new fuel entering the market.   

If BTC drops badly and sentiment turns - all market caps will lose $ value.