It does remain to be seen how important an (in-season) Young Driver's Test can prove to be. These have been quite low key affairs in the far flung reaches of the Middle East prior to this year. It's possible that not running at Silverstone in this test could be detrimental to Mercedes' season. It can't be stated with any amount of certainty how this scenario will play out. As suggested earlier, the weather could play a big part here as well.