While the current offer for x1 is supposedly scheduled to run through the holidays, I am 99% certain Microsoft will perminantely extend the $350 price after. And Sony, due to it's phenominal sales momentum, is likely to heavily bundle during the holidays, but may not see a need to reduce price.

My question is what affects will a price disparity between these machines cause long term? So say if the PS4 were to stay $50 more than X1 throughout 2015, what effect would that have on install base?

Presuming this does happen, predictions over the next year? 

Just to make sure, are you referring to WW or US only?

Its going to spike, almost match the PS4's holiday sales and then flatline come the end of the sale.

If it is US it will definitely make a difference-already seeing that now. However for MS to be competitive they need to drop the price to 300 euros in Europe at the very least

I'm interested in predictions for both, although I'm sure the effects would mostly be in the US. 

I saying if the 'sale' never ends.

I don't really see it making a difference seeing as how it needs to drop another $50 to become competitive. If they do that then I have no doubt they will change the landscape. There will be a small boost no doubt but I honestly don't think it will be enough to close the gap. Might win an NPD month or two but even that is an assumption made with high hopes and over-estimates the appeal of Halo.

So then you mean in the US. The WW victory is a forgone conclusion.  However,  in the states, the sales should be more even than this year.  However,  as you see with this year, Microsoft seems to put a wildly disproportionate amount of effort into their holiday linups; so you may get a situation where Sony is offering more compelling reasons to purchase during the rest of the year.  So we may wind up with a cycle where Sony pulls away after the holidays and Microsoft goes all in on the holidays,  and it may continue that way for anotheryear or two. 

Yeah, I'd agree with that.  Microsoft has gone all-in this month but in fact Halo MCC on November 11th may be the last XB1 exclusive for a long long time, at least based on currently announced release dates I believe no other XB1 exclusives have a release date.  So it's going to be a slow year after for XB1 until other games get some dates.

Whose to say that Sony wont have a holiday price cut of their own? Its not even the holidays yet and people are wondering where the Sony bundles and price cuts are.

But if Microsoft has a 50 dollar advantage on Sony, I just dont see it having a lasting effect without new games coming out on the platform. That is the major concern that I have for Microsoft come 2015.