You're being a bit pessimistic aren't you, JEM?
One of the reasons as to why this year's car has been somewhat uncompetitive is the botched up job done by Gary anderson, the chief designer last year. He was sacked early this year, but the car was already 80% complete, so the other designers didn't have enough time to redesign the poor aerodynamics on the car. Since then, Mark Handford and others have done a great job in trying to implement new aerodynamics to the car, which have greatly improved handling. The general feeling is that Jaguar should be able to get it right next year, and i believe they have potential for 20+ points next year. The engine is good this year(top 4 in ranking of power i believe), and i think Jaguar will be getting top-10 results before the end of the year. At Magny Cours, Irvine set his fastest lap on his first run (when the track wasn't clean) and spun in the other 3 runs. Had he kept the car on the track, he probably could have snared a top-10 spot easily. Don't worry, jaguar are on their way up...what you forget is that Jaguar is a 2 year old team and are on par with BAR, who are a 3 year old team. It took Ferrari years and years to set up their car to win a championship, and I think you shoudln't write off Jaguar's chances at all. They are capable of getting more than 5 points for the rest of the year...looking at their times in testing at Monza, they should go well.
One final thing, Irvine was unable to go better than 15th in qualifying at Silverstone, because he had to get into the spare car which was set up for De La Rosa, and didn't have the new floor. Irvine usually is 2 or 3 spots ahead of De La Rosa on the grid, De La rosa was 13th. He could have got 10th with more luck.