Detrimental.
Like Sony said, Microsoft are some greedy trolls. They'll steal anything!

(OK, since everyone decides to take these comments seriously I'll post this disclaimer... DON'T TAKE THIS TO HEART!)

They've both known each other's specifications for months now, almost certainly. No one is going to change anything major at this point just because of the other side revealed first.

E3 is still going to be the real battleground, regardless. I don't think this will matter much one way or the other.

I think the OP is talking about minor ajustments. Not major ones since we know that the nextbox and the ps4 will be pretty close.. again. 

Your cons list is messed up. Microsoft knows what is up with Sony, they don't need to watch the press conference to know if it's a beast or not.

Your pros list should include gimmicks. If both Sony and Microsoft are doing VR glasses for example, Sony gets credit for being the original.

It is a no brainier that this is a smart move for next gen. The ONLY negatives are for the PS3.

I think nothing will take away from the hype of a new PlayStation, the PlayStation brand has a much larger loyal fanbase than Xbox. They'll all want a new PlayStation no matter what news comes later. I don't feel like the Xbox name has that same following.

So... in other words, I think it's impossible to take away hype from the PS4 as long as there's that loyal fanbase guaranteed to be there day 1.

I don't think Sony will announce a price or the specs yet. More than likely they will talk about their plans for PS3 and PS Vita throughout the whole conference and last minute show the PS4 hardware (maybe a promo of a game or two) and leave the rest for E3.

Who says they'll need to outdo them? 360 is only half as powerful as PS3 according to Sony, and it was perfectly capable of running this gens games. Some games even better than PS3.

everything's to close to being final for any real changes.

Something along this lines, but with a little more info. For PS3 they will show demos and let the press play them, because they have a lot of stuff for the first part of the year. Hopefully they will reveal some titles for the PSVita (it really needs them).

For PS4, they will confirm that it will launch before the end of their fiscal year (march-2014), they will show some game demo videos, they will clearly state that the price will be affordable but no specific, they may not even show the control if it is the same as always, and of course tell that everyone and their dogs are creating games for the console (like with the Vita). And that is it. All the other information, like specs, price and official release date will be revealed at E3.

i doubt there is much benefit either way,regarding the actual console as i doubt you could change much in production but who knows

if it goes horribly in the media i guess its good,i mean you need good press don't you