I've highlighted the important parts. Wizards are the ones who determine what qualifies as a Product Line and what doesn't. Not your company. And this determination can change without warning.GSL part 6.1 said:6.1 OGL Product Conversion. If Licensee has entered into the “Open Gaming License version 1.0” with Wizards (“OGL”), and Licensee has previously published a product under the OGL (each an “OGL Product”), Licensee may publish a Licensed Product subject to this License that features the same or similar title, product line trademark, or contents as such OGL Product (each such OGL Product, a “Converted OGL Product”, and each such Licensed Product, a “Conversion”). Upon the first publication date of a Conversion, Licensee will cease all manufacturing and publication of the corresponding Converted OGL Product and all other OGL Products which are part of the same product line as the Converted OGL Product, as reasonably determined by Wizards (“Converted OGL Product Line”). Licensee explicitly agrees that it will not thereafter manufacture or publish any portion of the Converted OGL Product Line, or any products that would be considered part of a Converted OGL Product Line (as reasonably determined by Wizards) pursuant to the OGL. Licensee may continue to distribute and sell-off all remaining physical inventory of a Converted OGL Product Line after the corresponding Conversion is published, but will, as of such date, cease all publication, distribution and sale (and ensure that third party affiliates of Licensee cease their publication, distribution and sale) of any element of a Converted OGL Product Line in any electronic downloadable format. For the avoidance of doubt, (a) any OGL Product that is not part of a Converted OGL Product Line may continue to be manufactured, published, sold and distributed pursuant to the OGL; and (b) this Section 6.1 will survive termination of this Agreement.
If they chose to act in bad faith, they could declare every product published by your company as part of a single Product Line. Meaning all are covered by your signing of the OSL agreement. And all would have to change whenever the OSL was changed without warning. And all must permanently terminate publication without further sale when the OSL is terminated.