CDs/DVDs, No. They will certainly rot after two years or less as the tech stands today. It would not suprise me one bit however to pull out a hard drive 20 years from now that I store today and find it still accessable with all my data.
The only thing we can say with certainty is that there is no certainty. Which having written it is a bit of a contradiction, however, ho hum.
I think you will find that both of your statements are extremes, though I am sure you realise this. There are cases (as Didger has pointed out) where CDs are perfectly readable after 10 years - though if these are music CDs then they include a lot of error detection/correction algorithms to protect against fault data bits, data CDs do not and as such will not be so fault tolerant. Hard Disks are like any other magnetic media and degrade over time. Many large companies used to (and still do to a lesser extent) store back up data on magnetic tape in offsite storage, however, more often than not, when an old tape was retrieved the data was found to be corrupted.
The only way to overcome this problem is to continuously and regularly test your back ups. Keep two copies of the data backed up and if one of the backup media should show signs of failure then copy all the files onto a new media and throw away the old. As the only way to detect errors is not being able to read the archived file then a duplicate is required for recovery. This process is difficult to conduct with CD-ROM/DVD, hence the reason that more organisations are moving towards disc based systems - even if the archiving systems discs are unpowered (cold) most of the time.
All media will fail - archiving is not about which media the images are stored on, but the ongoing process of checking and replacing faulty media.
File formats and the ability to read data over a 10 year period is less likely to be an issue as there is so much equipment/data out in the world that needs to be supported from a legacy point of view. If you are following an archiving process that swaps out faulty media on a regular basis, then converting from one file format to another can be done at the same time. It is a case of getting away from a mentality of store and forget, towards one of constant maintenance.