Wix: How to limit major upgrades to major version numbers?

You need to use a NEW GUID for 2.x if you don't want it to be "aware" of 1.x (i.e. ignore it, don't care, etc)

I use the following code, only changing var.Property_UpgradeCode when I want a new version to ignore previously installed versions (e.g. exist side-by-side in different folders)

<Product Id="*"
         UpgradeCode="$(var.Property_UpgradeCode)"
         Name="!(loc.ApplicationName)"
         Language="!(loc.Property_ProductLanguage)"
         Version="$(var.version)"
         Manufacturer="!(loc.ManufacturerName)" >

<MajorUpgrade AllowSameVersionUpgrades="yes"
          DowngradeErrorMessage="!(loc.LaunchCondition_LaterVersion)"
          MigrateFeatures="no"
          Schedule="afterInstallInitialize" />

Put @Minimum and @Maximum attributes on a single UpgradeVersion element to specify a range. Author multiple UpgradeVersion elements to specify multiple version ranges.