No that is not right... they did not "limit" it to 4.7G, that is the standard for DVD Level 5
(Single Sided - Single Layer) media.
Many commercial DVDs are mastered using Dual Layer recording, to allow for more than 4.7Gig on a side,
but that is much harder (and more expensive) to pull off for a DVD Recordable drive. That is why
the current crop of drives will not support dual-layer recording, although there is work being done
to try and create consumer-level drives and media that is capable of doing so.
What does exist right now is media that allows recording on both sides of the disc
(Double sided - single layer), which gives you a little over 9 Gigs of capacity.
That is probably more useful for data storage than for backup copyies of your movies.