Interesting, I was just doing the Diesel vs petrol flip flop on ordering a new car.
In the end I decided petrol, my mileage isn't particularly high, about 10k but thats 99% Mon-fri commuting, we use the other halfs at weekends as its company where as mine is private on car allowance.
I was looking at all the hotish hatches (208 GTi, focus st etc), TT, 2 series etc. I spent a lot of time, too much really, looking into total ownership cost and found a few things,
some cars are truly terrible in depreciation, the worst I found was the Astra GTC, went from mid 20s to expected value of about £7.5k at 3 years 30k miles! Best was TT, 1.8TFSi losing just over 50% (28500 OTR to about 14200 expected at 3yr 30k)
Once I had ruled out the outliers (too slow, too thirtsy etc) I ended up with St3, TT 1.8Tfsi, Mini Cooper S JCW and Scirocco Tsi)
I again checked the diesels on those ranges and again came to the conclusion that the residuals meant the cost of ownership lent me towards petrol. I found the site
www.fleetnews.co.uk was accurate for residuals etc when comparing to manufacturers finance (which is an easy way to look at expected depreciation). If I was doing 20K+ I would still look diesel, but at lower mileage and unsure if I would want the car in 3 years it seemed better to go petrol. The MPG is an issue but I only pay the tax on my fuel as BIK, company picks up the cost so its less an issue to me.
I eventually had to decided between St3 and TT, was a hard choice but I felt the TT just pipped the St on a lot of soft measures so went that way. Got just under 20% off list price so cant grumble

The JCW was a serious contender and had I not have had a gen 1 and 2 new mini I would have struggled to not pick that to be honest, but just wanted something different. If I needed seats the St3 would have been the pick, but I dont, 99% of the time its just me in there going to work and back.
Separate but my work collegue is looking for a Jag XE petrol, they pretty much don't exist second hand. He found 1 with a half decent spec, where as there are loads and loads of diesels.
In conclusion I don't see there being any real diff to diesels in the next 3-5 years, residuals have probably tanked too hard. New car sales of petrols will increase and supply/demand will balance back again.