Didn't get the PS3 until about a year after launch; I already had a 360 and waited until there were at least a few exclusives I wanted so I wasn't just doubling up. Chances are the same thing will happen this time too; especially as a lot of the PS4's first batch of games will likely be on this gen's machines as well.
PS4: Waiting until Black Friday 2015. I still have a lot of PS3 games to play. If online is free for PS4, I'll be tempted even earlier, just want to wait for a larger hardisk at least 500 GB and software bundled with it, maybe "God of War IV" or "Ratchet and Clank..". I really want a collectible bundle if possible.
PS3: 60 GB fat with BC, for $499.99 in summer (August of '07). Gamestop just lowered the price and I heard that the new models had limited BC. I also sent the in for 4 or 5 free Blue Ray movies ("Invincible", "Blazing Saddles", Stir of Echoes" and at least one other. At the time, Bllu-Ray movies were very expensive, so an 80 value".). I also paid $50 or $60 dollars for a 2nd sixaxis controller and $60 for "Resistance..", "Ratchet and Clank: Tools" and "Heavenly Sword".
PS2: 1 year after launch. The price didn't even go down: still $300, but had to play "MGS:2", it was also my first DVD player and definitely got my money's worth over a decade.
PS1: $299.99 on launch day: 11/95 in US. Traded in my entire SNES collection:(. I later re-bought most of the collection for a fraction more. The PS1 died and I upgraded to a Dual Shock edition for $199.99. Later bought a PSone with the 4.75 inch screen. Really wanted a portable gaming device, a year before the GBA SP came out and fixed that problem.
I'm going to have mine pre-ordered the first day it's available. Now, if I keep the pre-order and actually pay it off is up to what Sony show's at E3. If they have a good showing, some good legitimate info get's released, and it's nice outrageously prices (over $600) then I'll have mine day 1.
Bought PS2 at launch (was on local news t.v. airing for it actually), which killed my "I'm sick excuse" that I used to miss school -- whoops.
Bought PS3 in 2011 when I got a good Sony Visa credit card deal and system modding became possible. After going through three PS2 for failed drives, I wanted to be sure that I could continue playing my PS3 even if the drive crapped out.
With PS4 looking to be a PC, I don't think I will get one. I'd rather just stick with my Wii U, PS3, and get a gaming PC again if need be. That or a Steam Box.
1st PS3 Launch - Died in 09 2nd PS3 November 2012 - Playing catch up with the games that I missed
I predict that will not be buying a PS4 until, at least, two years after launch. This gen (and all of its problems) have soured me from buying launch systems. This comes from someone who been getting launch systems since the NES days.
PS1 bought in summer of 1998 PS2 got for X-Mas in 2001 PS3 bought May 2007 (60 GB) PSP bought in 2007 PS3 (60 GB) died in November of 2009 PS3 (Slim 320) bought in December of 2009 PS Vita bought the First Edition Bundle in Feb. 2012 PS4 will buy day 1