I'm Swedish so here's a better translation than Google Translate.
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Those who wait for the 20 nm generation will have to wait a while further. According to information which Sweclockers has received, the Maxwell architecture will stay at 28 nm all year this year.
In the middle of February this year, Nvidia launched the first graphics processors with the architecture Maxwell. The new generation was initiated with the budget class cards Geforce GTX 750/750 Ti, which means that the older architecture Kepler still reigns in the higher performance classes.
Despite this, the new architecture will still use 28 nm.
Although TSMC is in production using 20 nm, it does not look like it will be applicable to high performance ciruits required for graphics processors(This means that we're looking at 28 nm for all classes, not just high end GPUs - Ed). This has affected Nvidia's future plans.
Taiwanese partners are now telling Sweclockers that it will take a while before Nvidia can introduce GPUs with the Maxwell architecture. In best case scenario(my italic) we may see a very selected few models, but more likely is the case that we'll have to wait until some time into 2015.(Note: not right away, but "some time into", meaning we may be looking at Q2 in 2015 -Ed)
A transition from 28 nm to 20 nm is viewed as required(my italic. So no "soft launch" then) for Nviida to use Maxwell in the higher performance classes. This is especially the case for the successor to the monster GK110, which is the foundation for 780, 780 Ti and Titan/Titan Black.
That 20 nm will be delayed can also explain why the first GPUs with Maxwell did not constitute a new series but are now forced to cohabitate with the current Kepler 700-series.