Here's a site that calls itself The Sikhism Homepage. It does not mention any links to Islam, or links to Muslim practices. In fact, it specifically says it is not in any way related to Islam. It also says it is not in any way related to Hinduism, so I may have been wrong in that respect.

What I find noteworthy in this site... Sikhism :History, beliefs, practices, etc. (Religious Tolerance.org)

...is this part...

"An invasion by Great Britain triggered the Sikh Wars (1845-1849). The British successfully gained control over all of India. After independence in 1947, occupied India was partitioned on religious grounds into a mostly Muslim Pakistan and mostly Hindu India. A mass migration of Sikhs from Pakistan to India and a reverse migration of Muslims resulted, with immense loss of life. Some Sikhs have been seeking an independent homeland since the late 1940's."

The fact that the Sikhs left Pakistan and moved to India suggests that this sentance by you...

Gradually the Sikhs took on more Moslem traits until they could better be called an offshoot is Islam.

Is probably incorrect.