The average value of electronic control units has jumped from $550 to $650 between 2002 and 2008. If and when the economy recovers, the content is likely to start increasing again, especially as vehicle electrification becomes more prevalent. Not only will the powertrains and batteries need electronics, but the move to systems like electric power steering and air conditioning will also require ECUs.
Eventually, as all of these systems become ubiquitous, the value growth will again slow and then decline as a result of decreased costs of electronics.
[Source: Automotive News - Sub. req'd]