How about confirming with the CIC call centre? Below is what they sent me when I had requested information about implied status - Note the part in red - you are going from 'semi-skilled worker' to 'skilled worker' and eventhough it's the same employer that is a change in conditions of your previous permit so you must stop working until you receive the new permit, unless you receive written information from the call centre otherwise.
"Sir, Madam,
Thank you for contacting the Call Centre. I am pleased to provide you with the requested information:
As a temporary resident, if you send your application for an extension of your authorization to remain in Canada at the latest on the expiry date of your status, you will be considered in status as a temporary resident until a decision is made on the application. This is known as an Implied Status.
If you hold a work permit or a study permit, you can continue working or studying under the conditions of your previous permit if you have applied to extend your stay in Canada under the same category. However, if you have applied to extend your stay under another category, you must stop working or studying.
If you leave Canada while under implied status, you may be authorized to:
•re-enter Canada as a temporary resident, if the Case Processing Centre (CPC) in Vegreville, Alberta, has not yet made a decision on your application to extend your work/study permit. Please note that you will not be permitted to work/study until you receive your new permit. You must satisfy the officer at the port of entry that you have sufficient means of support. This applies if you:•are temporary resident visa (TRV) exempt;
•held a valid multiple-entry visa before leaving Canada; or
•travelled only to the United States and/or St.Pierre and Miquelon;
•re-enter Canada as a worker/student, if the officer at the port of entry determines that your application to extend your work/study permit was approved by the CPC while you were outside Canada;
or
· apply for a new work/study permit at the port of entry provided you have the right to do so under the Regulations.
For more information on implied status, please see OP 11, section 24 of the Operational Manuals.
The Internet links below will provide you with more detailed information:
Description: Overseas Processing - see OP 11, section 24
Address: http://www.cic.gc.ca/english/resources/manuals/op/index.asp
Description: Eligibility to apply for a Work Permit as you enter Canada
Address: http://www.cic.gc.ca/english/work/apply-who-eligible.asp#enter
Description: Eligibility to apply for a Study Permit as you enter Canada
Address: http://laws.justice.gc.ca/eng/SOR-2002-227/page-7.html#anchorbo-ga:l_12-gb:l_2. "