The Year 5 tests were proposed by Professor Richard Daugherty's assessment review group in 2004, in a package of measures that resulted in the abolition of national testing at 11 and 14 in Wales.
The new externally-marked tests in literacy, numeracy and problem-solving are expected to help children with transition from primary to secondary school.
Jane Davidson, education, lifelong learning and skills minister, said 21 months ago that test materials would be tried out "in a small number of schools" in 2005-06.
But with Easter late and the summer term short, primary heads say they have heard nothing more. Ms Davidson intended the tests to be piloted in all schools by 2006-07 before they become a legal requirement in 2007-08.
ACCAC, the now-defunct Welsh qualifications, curriculum and assessment authority, has carried out research at home and abroad "into the nature and purpose of such tests". The research has been presented to the Assembly government, which declined to release it to TES Cymru.
A government spokesperson said: "Detailed proposals will be based on consideration of (the research). The new arrangements will be subject to wide consultation and detailed piloting ahead of roll-out from 2008."
Stuart Broomfield, a senior adviser with ESIS, the education and school improvement service for four south Wales LEAs, said: "I don't know where we are on skills tests. It has gone very quiet."
Gwilym Jones, head of Ysgol y Wern, Ystalyfera, Neath Port Talbot, welcomed diagnostic skills tests, but said: "We haven't heard a dickie bird as to what's happening. If schools are to administer these tests, we need to know now."